Concentrated X-ray contrast media can act as universal antigens and can inhibit or prevent allergic reactions

ABSTRACT

The present application is directed to the use of X-ray contrast media that act as universal antigens that are labeled herein as “pseudoantigens.” X-ray contrast media have the potential to exist in an aggregated state that is greater in increased concentrations. In this aggregated state, contrast media assume the role of multivalent antigens and can successfully compete with any other antigens involved in antibody-antigen reactions that lead to anaphylaxis. In this competition, the large quantity of contrast media serves to inhibit the adverse effects of antibody-antigen reactions without the contrast media itself creating antibodies or creating toxicity problems.

RELATED APPLICATIONS

[0001] This patent application is a continuation of PCT ApplicationSerial No. PCT/US02/32467, filed on Oct. 10, 2002, entitled“Concentrated X-ray Contrast Media Can Act as Universal Antigens and CanInhibit or Prevent Allergic Reactions,” which application claimspriority under 35 U.S.C. § 119(e) to U.S. Patent Application Serial No.60/329,027 filed Oct. 12, 2001; both of which are hereby incorporated byreference in their entireties.

Background of the Invention

[0002] 1. Field of the Invention

[0003] The present invention is generally directed to the use of X-raycontrast media to block antigen-antibody complexes. The presentinvention is more specifically directed to the use of contrast media asdrugs to inhibit allergic reactions, to treat or prevent allergicconjunctivitis, allergic rhinitis, their use in “rush” and “routine”immunotherapy and in non-responding anaphylaxis.

[0004] 2. Description of the Related Art

[0005] It has been known for many years that individual X-ray contrastmedia (“CM”) have a varying potential to produce reactions that resemblein every respect the anaphylactic reactions that occur in someindividuals subjected to antigens to which they have a knownhypersensitivity (Shehadi, W. H., AJR 1975, 124, 145-152; Lasser, E. C.et al., Radiology 1997, 203, 605-610; Katayama, H. et al., Radiology1990, 175, 621-628). X-ray contrast media reactions, however, occur inindividuals regardless of previous exposure, and no one has been able toreliably demonstrate the presence of specific antibodies in thesepatients or in experimental animals injected with any of the contrastmedia unless these media were artificially bound to a protein prior toinjection (Carr, D. H. and Walker, A. C., Br. J. Radiology 1984, 57,469-473; Brasch, R. et al., Invest Radiology 1976, 2, 1-9; Lasser, E. C.et al., AJR 1962, 87, 338-360; Dunn, C. R., Lasser, E. C. et al., InvestRadiology 1975, 10, 317-322). While previous exposure to contrast mediais not necessary for a patient to develop a reaction, reactions occurmore commonly in individuals with a history of an allergy of any sort(Katayama, H. et al., Radiology 1990, 175, 621-628; Lasser, E. C. etal., Radiology 1997, 203, 605-610). Most (non-contrast media) clinicalallergic reactions occur when a person is exposed to an antigen havingthe molecular properties of a protein or of a smaller molecule that canbe shown to bind to a protein in vitro (a “hapten”). X-ray contrastmedia have neither of these attributes. Some out-of-date mediademonstrated a degree of binding to some serum proteins, but this wasnever sufficient to allow the media to act as haptens (Lasser, E. C. etal., AJR 1962, 87:338-360). In light of these considerations, thereactions that sometimes occurred after contrast media injections weretermed “anaphylactoid” rather than true “anaphylaxis.” True“anaphylaxis” is known to require the release of histamine and othermediators present within either mast cells or basophilic cells. Theformer can be found within tissues while the latter are present in theblood stream. While it could be demonstrated that histamine releaseoccurs in X-ray contrast media reactions (Lasser, E. C., Walters, A. J.,et al., Radiology 1971, 100, 683-686; Siegle, R. L. and Liebennan, P.,Invest Radiology 1976, 11:98-101), the exact mechanism by which thisoccurred has, until recently, been obscure.

[0006] Employing a highly sensitive test for antibody-antigen complexing(passive red blood cell hemagglutination inhibition), we found what weconsider the answer to this problem. Ovalbumin and gamma globulin(Sigma) were bound to glutaraldehyde stabilized sheep red blood cells(Inter-Cell Technologies, Hopewell, N.J.). Bis-diazotized benzidine wasused to bind the ovalbumin to the RBC's. The gamma-globulin bounddirectly. In both the case of the ovalbumin and the gamma-globulin, thesensitized red blood cells were allowed to incubate with each of thecontrast media (methylglucamine iothalamate [CONRAY; 282 mg iodine/ml,Mallinckrodt Medical, St. Louis Mo.], ioversol [OPTIRAY 320; 320 mgiodine/ml, Mallinckrodt], IOXAGLATE [HEXABRIX; 320 mg iodine/ml,Mallinckrodt] and IOTROLAN [ISOVIST; 300 mg iodine/ml, ScheringPharmaceutical; Berlin, Germany]) and the antibodies at room temperaturefor 2-3 hours prior to evaluation of the potential of the contrast mediato compete with the bound ovalbumin or gamma-globulin for theirrespective antibodies and thereby to function as “pseudoantigens.” If nocompetition occurred, there would be a visible agglutination thatcovered variable areas of the base of the microtiter well, dependent onthe strength of the antibody titer. When competition occurred, therewould be a diminished diameter of the agglutination, depending on theantibody titer that could be compared to a control, where saline wassubstituted for the CM. With complete competition (inhibition), noagglutination would be visible and the RBCs would form a small button ofcells at the bottom of the microtiter well. Visible agglutination wasevaluated on a 1+ to 4+ basis. Studies were also carried out where theRBCs were incubated with CM before or after binding of the antigen toBDB or the RBC to determine whether competition of the CM with theantigen might actually represent displacement of the CM from the RBCsurface.

[0007] It was discovered that contrast media can in fact act as anantigen and combine with antibodies (Lasser, E. C. and Lanakin, G. E.,Academic Radiology 1998, 5 (suppl. 1; S95-S98)). This was shown when, atvarious concentrations, individual contrast media would inhibit theagglutination of RBC-attached ovalbumin or RBC-attached gamma globulinin the presence of their respective antibodies, thus resulting in abutton of cells, rather than agglutination, in the bottom of themicrotiter well. Table I shows the results of this experiment. TABLE Iγ-globulin vs. anti-γ-globulin Lowest concentration of CM showing a 2+or 3+ inhibition of 1/500 IgG anti-γ-globulin mg/ml HEXABRIX 8.0 ISOVIST14.0 OPTIRAY 16.0 Mga LOTHALAMATE 28.2 Na LOTHALAMATE 28.2

[0008] The results shown in Table I demonstrate that various contrastmedia compete successfully for binding to the antibodies awaiting theRBC-antigens and thereby rendering the antibodies unavailable to theseantigens. Further studies indicated that this occurred most readily inconcentrated CM solutions and that most of the contrast media currentlyin use tend to aggregate to varying degrees and this was particularlytrue in more concentrated solutions.

[0009] Ovalbumin is known to bind on the variable portion of theimmunoglobulin molecule (Fab), while gamma globulin is known to bind tothe constant portion of the specific immunoglobulin (Fc)(Frick, O. L. inBasic & Clinical Immunology 2nd Edition, Fudenberg, Stites, Caldwell andWells editors; Lange Medical Publications; Chapter 22; ImmediateHypersensitivity). Later, the potential of a contrast molecule tocompete with ragweed pollen in a ragweed sensitized in vivo rat model(and thereby inhibit the development of ragweed pollen conjunctivitis)was tested. The available data thus far suggests that with localapplication, the contrast molecule utilized (IODIXANOL; Nycomed, Oslo,Norway) provides a degree of protection by successfully competing withthe local application of ragweed antigen and thus inhibiting thepotential of the antigen to bind with its specific binding site onanti-ragweed-IgE attached to conjunctival mast cells (see Example V).Thus, it is demonstrated that contrast media have the potential to bindto at least three divergent antibodies and furthermore (inferentially)that binding may take place on either the constant, variable, or boththe constant and variable portions of the immunoglobulin molecule.

[0010] In the literature, there is a report suggesting that contrastmedia in vivo reduced the binding of three diverse tumor antigens totheir respective antibodies, and thereby falsely lowered the testedblood concentrations of these antigens (Watanabe, N. et al. Nucl. Med.Commun. 1998, 19:63-70). The mechanism for this was not explored in thearticle, but a careful review of the publication demonstrates that it islikely that the various contrast media were interfering with the abilityof the tumor antigens to bind to their respective antibodies.

[0011] In view of all of the above information, it is believed thatcontrast media function as totipotential universal antigens and maythereby compete with any antigen for binding sites on its specificantibody.

[0012] Since contrast media, like antigens, can bind to antibodies butcannot themselves produce antibodies (unlike antigens), we have termedthe contrast media “pseudoantigens.” It was noted earlier that thecontrast media do not have the chemical characteristics to bind tomacromolecules and thus do not have attributes to function likeclassical antigens. The question then arises: how then, do contrastmedia compete with antigens? In discussing this issue, it is necessaryto have information on the general structure of contrast mediamolecules.

[0013] The X-ray contrast media currently available are generallytriiodinated, completely substituted, benzene moieties existing in theform of a monomer or a dimer. These contrast media molecules may beeither ionic or nonionic (or in the case of one dimer, part ionic andpart nonionic). There are generally slight variations in the amide sidechains attached at the 3 and 5 positions on the ring and in the natureof the cations (for the ionic media) and there are slight differences inthe length of the aliphatic chains linking the dimers and in the natureof the coupler group.

[0014] Some examples of X-ray contrast media that are commerciallyavailable are METRIZAMIDE, IOPAMIDOL and IOXEXOL which are nonionicmonomers. IOXAGLATE and IOTROLAN are ionic dimers. For purposes of thispatent application, only nonionic dimers will be considered. The onlytwo ionic dimers believed to be commercially available thus far areIODIXANOL and IOTROLAN. The term “mammal” as used herein refers to humanand non-human mammals. Within certain embodiments of the invention,dosage of CM may be from 0.1-40 grams of CM depending on the subject tobe treated and the CM. Other dosages of administered CM may be from0.01-0.1 grams, 0.1-5 grams, 5-10 grams, 10-15 grams, 15-20 grams, 20-25grams, 25-30 grams, 30-35 grams, 35-40 grams, 40-45 grams, 45-50 gramsand 50-100 grams.

[0015] The ability of the contrast media to bind to antibodies mustdepend on some factor other than their chemical composition since, asnoted, their molecular structures do not suggest a potential for bindingand in dilute solutions, no binding to globulins could be demonstrated(Lang, J. H. and Lasser, E. C., Invest Radiology 1967, 2:396-400). Theexplanation appears to be the potential of all of the contrast media, inrelatively high concentrations, to aggregate, as determined by bothphysical-chemical analysis, and by comparing theoretical vs. actualosmolalities (Krause W., et al., Invest Radiology 1994, 29:72-80;Schneider, P., European Radiology 1996, 6:15-16). In an aggregated form,contrast molecules have physical characteristics that simulate amultivalent antigen. In considering the aggregation phenomena it turnsout, counter-intuitively, that the best aggregators, and the bestantibody binders, are also the contrast media least likely to produceadverse reactions on injection into animals or humans. Under normalcircumstances one would expect that the molecule most likely to promoteantibody-antigen reactions would be the molecule most likely to play arole in adverse reactions.

[0016] In attempting to solve this paradox, a study done much earlier inour laboratory is referenced, wherein dogs injected with a constantvolume of contrast media over either a 2 second or 10 second intervalconsistently produced a higher concentration of histamine release withthe longer interval (Lasser, E. C. et al., Radiology 1971, 100:683-686).

[0017] Histamine release from mast cells and basophils is known to occurwhen adjacent IgE antibodies attached to these cells are connected by abridging antigen. Under these circumstances, the receptors that bind theantibodies to the cells are believed to be activated to inducephospholipid methylation and an increase in intracellular cyclic AMP.These biochemical events are followed by an influx of calcium and therelease of histamine (Ishizaka, T. et al., J Immunology 1983,130:2357-62). Given these facts, it appeared paradoxical that the faster(2 sec.) injection which should have presented the antibodies on thecells with a higher concentration of contrast media and thus a higherconcentration of “pseudoantigens” (and hence greater histamine release)actually resulted in less histamine release than the slower injection.

[0018] Further analysis of this paradox pointed to the phenomenon of“antigen-excess.” Antigen-excess in vitro has been recognized for manyyears (Myrvik, Q. N. and Weiser, R. S. —Fundamentals of Immunology,Second Edition: Lea and Febiger, Philadelphia 1984, 96102). When asufficiently concentrated antigen is added to a solution of its specificantibody, there will be successive phases of antibody-excess,antibody-antigen equivalence and finally antigen-excess. In most casesat antibody-antigen equivalence, a precipitate will develop. Inantigen-excess, soluble compounds (antigen-antibody complexes) willremain in solution in the supernatant so that precipitation is less thanmaximal. With a large excess of antigen, inhibition of precipitation maybecome complete. FIG. 3 depicts our interpretation of the antigen(“pseudoantigen”)-excess phenomenon as it applies to CM binding to IgEimmunoglobulins on mast cells.

SUMMARY OF THE INVENTION

[0019] The present invention is directed to the use of contrast media ormodified contrast media molecules (for example contrast molecules withthe iodine removed—see FIG. 7B) as drugs that can be utilized to inhibitallergic reactions. The toxicity of the contrast media that is proposedis very low in comparison to almost all drugs on the market and thedetails of the toxicity of these substances are well known throughextensive utilization and research. The contrast media that are proposedare in the dimer and nonionic form and thus are known to be the leasttoxic of contrast media.

[0020] Some possible applications of these “rescue” molecules have beensuggested in the body of this application. They will include explorationof their application in human allergic conjunctivitis and in allergicrhinitis. They will also include exploration of their use in statusasthmaticus, in “rush” immunotherapy and in routine immunotherapy. Apossible use in non-responding cases of anaphylaxis will also beconsidered. In all of these applications the ability of the contrastmolecules to constructively compete with known antigens for theirrespective antibodies should reduce the number of times when allergicevents result in serious consequences. All of this can be accomplishedwithout fear that the contrast molecules will themselves result in theproduction of antibodies.

[0021] Aspects of the present invention are described in the paragraphsbelow:

[0022] 1. The use of X-ray contrast media to inhibit, treat or preventan allergic reaction in a mammal suffering from an allergic reaction byadministering X-ray contrast media to such mammal.

[0023] 2. The use of paragraph 1 wherein the X-ray contrast mediainhibits, treats or prevents an allergic reaction by blocking adverseantigen-antibody complex formation.

[0024] 3. The use of paragraph 1 wherein the X-ray contrast media isselected from the group consisting of dimeric nonionic contrast media ordeiodinated nonionic contrast media derivatives.

[0025] 4. The use of paragraph 1 wherein the X-ray contrast media are ina dimer form.

[0026] 5. The use of paragraph 1 wherein the X-ray contrast media isnon-ionic.

[0027] 6. The use of paragraph 1 wherein the X-ray contrast media are inan aggregated form.

[0028] 7. The use of paragraph 1 wherein the X-ray contrast media areadministered in a manner selected from the group consisting ofsubcutaneously, intramuscularly, intravenously or topically.

[0029] 8. The use of paragraph 1 wherein the X-ray contrast media aretriiodinated, completely or partially substituted, benzene moietiesexisting in the form of a monomer or a dimer.

[0030] 9. The use of paragraph 1 wherein the antibody is selected fromthe group consisting of IgA1, IgA2, IgD, IgE, IgG1, IgG2, IgG3, IgG4 andIgM.

[0031] 10. The use of X-ray contrast media for treating anaphylaxiscomprised of the step administering from 0.1 grams to 40 grams of X-raycontrast media to a person suffering from any form or degree ofanaphylaxis.

[0032] 11. The use of paragraph 10 wherein the contrast media is anydimeric nonionic contrast media.

[0033] 12. The use of paragraph 10 wherein the X-ray contrast media isadministered subcutaneously in antigen desensitizing therapy to inhibitlocal or systemic anaphylaxis resulting from the desensitizing antigen.

[0034] 13. A method of preventing adverse in vivo antigen-antibodycomplex formation by administering from 0.1-40 grams of X-ray contrastmedia to a person.

[0035] 14. The method of paragraph 13 wherein the X-ray contrast mediais selected from the group consisting of dimeric nonionic contrastmedia.

[0036] 15. A method of treating or preventing allergic conjunctivitiscomprised of the steps of administering from 0.1 to 3 ml of dimericnonionic X-ray contrast media to an eye suffering from allergicconjunctivitis.

[0037] 16. The method of paragraph 15 wherein the X-ray contrast mediais selected from the group consisting of any dimeric nonionic contrastmedia.

[0038] 17. The method of paragraph 16 wherein the X-ray contrast mediais selected from the group consisting of IOTROLAN and IODIXANOL.

[0039] 18. The method of treating allergic rhinitis by administeringfrom 0.1 to 3 ml of a dimeric nonionic contrast media by dropinstallation into the nose in a mammal suffering from allergic rhinitisor exposed to a known potential nasal allergen.

[0040] 19. The method of paragraph 18 wherein the X-ray contrast mediais a dimeric nonionic CM.

[0041] 20. The method of paragraph 19 wherein the X-ray contrast mediais selected from the group consisting of IOTROLAN and IODIXANOL.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042]FIG. 1 shows the structures of some commercially availablecontrast media;

[0043]FIGS. 2A-2B show histamine release in response to injections ofcontrast media;

[0044]FIG. 3 illustrates the phenomenon of antigen excess;

[0045]FIG. 4A shows the rise in blood pressure in Brown-Norway andSprague Dawley rats following the bolus injection of 5 mg/kg ofdiphenhydramine;

[0046]FIG. 4B shows that in 15 tested animals, injection of L-Name, anitric oxide inhibitor, produces a rise in BP and that ISOVIST no longerproduces a rise in blood pressure when the production of nitric oxide isblocked;

[0047]FIG. 5 shows that the injection of a CM dimer along with OVA in 5OVA-sensitized rats (diamonds) diminishes the prolonged fall in bloodpressure that results from injection of OVA and saline made equiosmolarto the dimer in 4 sensitized rats (squares) which results fromantigen-specific, antigen equivalent immunogenic mechanisms having tocompete with the pseudoantigen, antigen excess mechanisms operative whenthe CM accompanies the OVA;

[0048]FIG. 6 shows IODIXANOL vs. control treatment given 10 minutes postchallenge in sensitized Sprague Dawley rats;

[0049]FIG. 7 shows the structural formula IODIXANOL;

[0050]FIG. 8A shows the structural formula of deiodinated IODIXANOL; andFIG. 8B shows the structural formula of IOTROL.

DETAILED DESCRIPTION OF THE INVENTION

[0051] The phenomenon of antigen-excess has never before been consideredin vivo. However, no other intravascular drug is administered at onetime in the amount that the contrast media are administered (up to asmuch as 45 grams in a single injection, etc.). It is believed that thepresence of antigens in excess inhibits the likelihood of a singleantigen to find empty binding sites on adjacent IgE antibody moleculesand thus to produce the release of histamine. An alternative possibilityis that the aggregated CM fill the space between adjacentimmunoglobulins and prevent the approximation of these molecules and/ortheir receptors by virtue of steric hindrance. Therefore, the more rapidinjection of the contrast media in the dogs is believed to have producedan antigen excess situation relative to the existing IgE antibody on thecells of the dogs from previous sensitization episodes and thus producedless, rather than more, histamine release. Correspondingly, it would nolonger appear paradoxical that the contrast media exhibiting the bestpotential to compete with specific antigens for antibody binding sitesin our study of passive hemagglutination inhibition would in fact be themedia less likely to produce adverse reactions, rather than theopposite.

[0052] Given the above considerations, the question was asked whethercontrast media with less potential to compete with antigens in ourpassive hemagglutination inhibition studies would be more likely toattain antibody-antigen (pseudoantigen) equivalence rather than antigenexcess in vivo, and thus be associated with a higher incidence ofadverse reactions. This is the case in clinical studies since the ionicmonomers, the nonionic monomers, and the nonionic dimers, in that order,needed higher concentrations of concentration-equivalent contrast mediato inhibit hemagglutination and range from most toxic to least toxic inthe same order. It is thus necessary to consider that the media that aremore commonly associated with reactions will be those that are lesslikely to inhibit hemagglutination in our test and/or are injected in afashion to produce more dilute contrast solutions.

[0053] The significant adverse reactions occurring with contrast mediaare usually associated with histamine release and a drop in bloodpressure. To test the effect on blood pressure in a series of rats, thearterial pressure was monitored following the injection of variouscontrast media at different concentrations (Lasser, E. C. and Lamkin, G.E. Academic Radiol, 2002, 9 [suppl. 1], S72-S75). These studies weredone since it is accepted that the release of histamine from mast cellsand/or basophils results in a blood pressure lowering effect. Basalendogenous ongoing histamine release thus effects the prevailing bloodpressure and events that increase or decrease histamine release will beassociated with a decreased or increased blood pressure.

EXAMPLES Example I Blood Pressure Changes as an Index of HistamineRelease

[0054] Sprague Dawley and Brown Norway rats (300-350 g) were purchasedfrom Harlan Sprague Dawley (Indianapolis, Ind.). The CM utilized weremeglumine/sodium diatrizoate, an ionic monomer (ANGIOVIST 370; 370 mgI/ml; Berlex Laboratories, Wayne N.J., USA), meglumine iothalamate, anionic monomer (Conray; 282 mg I/ml; Mallinckrodt Medical, St. Louis,Mo., USA), IOXAGLATE, an ionic dimer (HEXABRIX; 320 mg I/ml; GuerbetLaboratories Aulong-sousBois, France), IOPAMIDOL, a nonionic monomer(ISOVUE 300; 300 mg I/ml; Bracco Pharmaceuticals, Milan, Italy),IOTROLAN, a nonionic dimer (ISOVIST; 300 mg I/ml; ScheringPharmaceuticals, Berlin, Germany), and IOVERSOL, a nonionic monomer(Optiray 240; 240 mg I/ml, Mallinckrodt). The monomers are either ionicor nonionic molecules consisting essentially of a tri-iodinated fullysubstituted benzene ring. The dimers are two such benzene ringsseparated by an aliphatic chain. A Propaq blood pressure monitor(Protocol Systems, Beaverton, Oreg., USA) was connected to polyethylenecatheters inserted into a carotid artery and measured mean arterialpressures. Injection rates into a tail vein varied from 2 to 8ml/kg/min. Modifications of the mean blood pressure tracings inindividual animals were studied by injections of the followingsubstances either preceding or following the CM. NG-nitro-L-argininemethyl ester (L-NAME; Sigma), sodium nitroprusside (SNP; Sigma),histamine (Sigma), phenylephrine (Sigma), phentolamine; (Sigma),L-arginine (Sigma), diphenhydramine (Benadryl; Sigma), and BQ 123(American Peptide Co., Sunnyvale, Calif., USA).

[0055]FIG. 4A shows that the infusion of an H-1 blocker(diphenyhydramine) in the rats produced an immediate elevation in bloodpressure. The injection of L-NAME, the L-arginine analog that blocks theproduction of nitric oxide, also produced an immediate elevation inblood pressure (FIG. 4B). It is also worth noting that the injection ofa nonionic contrast media dimer (ISOVIST), when injected by itself,produces an elevation in pressure, can no longer produce an elevation inblood pressure when the production of nitric oxide is blocked. This isevidently due to the fact that the dimer elevates pressure by blockingongoing IgE mediated histamine/nitric oxide release and hence theirvascular dilating effect, but can not evidence this when nitric oxiderelease is already blocked. The results of Example I are described belowin Table II. TABLE II Net increase/decrease in mean arterial bloodpressures in the Brown-Norway and Sprague Dawley rats are summarizedbelow Brown Norway Rats Sprague Dawley Rats Contrast media: mm Hg (mean± S.E.) mm Hg (mean ± S.E.) Monomers (4 ml) Conray decrease (37 ± 1.6)(3) decrease (55 ± 5.0) (3) Optiray decrease (20 ± 1.5) (3) NO DATAMonomers (8 ml) Isovue decrease (36 ± 8.6) (2) decrease (27 ± 8.6) (2)Optiray decrease (33 ± 2.8) (3) decrease (22 ± 0.0) (1) Angiovistdecrease (40 ± 0.0) (1) NO DATA Dimers (4 ml) Isovist increase (18 ±0.00 (1) NO DATA Dimers (8 ml) Isovist increase (20 ± 2.0) (4) increase(11 ± 4.6) (3) Hexabrix increase (31 ± 4.6) (3) NO DATA

[0056] As the above results demonstrate, monomers produced a net fall inblood pressure while the dimers produced a net elevation of bloodpressure. In most experimental and clinical studies, CM injections havebeen associated with a reduction in blood pressure so it came as nosurprise that the monomers produced a net fall in blood pressure. Thefact that dimers produced a net elevation in blood pressure was asurprise and was contrary to expectations.

[0057] In attempting to understand why a blood pressure elevation wasobtained under our experimental circumstances it was considered whatwould happen to blood pressure in these animals if the histaminereceptor (H-1 receptor) was blocked. It was found that this consistentlyproduced a pressure elevation lasting about 20 minutes (see FIGS.4A-4B). In another publication, it was noted that nitric oxide, as amediator released by histamine through activity at the H-1 receptor,played a role in lethal dose studies in rats and that blocking theproduction of nitric oxide increased the amount of contrast that a ratcould accept before lethality (Lasser, et al., Academic Radiology 1995,2, 559-564). When the production of nitric oxide was blocked (utilizingL-NAME, a nitric oxide analog), a blood pressure elevation was producedsimilar in all respects to that produced by blocking the H-1 receptor(see FIGS. 4A and 4B). The same findings occurred in the presence ofsalient blood pressure modifiers (phenylephrine and phentolamine)(Lasser E C and Lainkin G E Academic Radiology 2002; 9 [suppl 1];S72-S75). Since, as noted, injections of the dimers produced bloodpressure elevations and these could be blocked by L-NAME, it wasconcluded that the blood pressure elevations in these circumstances weredue to an antigen (pseudoantigen) excess effect that effected(inhibited) endogenous ongoing histamine and nitric oxide releaseresulting from endogenous antigens interacting with their specific IgEantibodies on mast cells and basophils.

Example II Effect of Dimeric CM on Blood Pressure Changes in Anaphylaxis

[0058] To further substantiate the concept that contrast media, actingas pseudoantigens, could interfere with existing antigen-antibodyreactions, an experiment was conducted where a series of rats weresensitized to ovalbumin and later challenged the rats by intravenousinjections of ovalbumin.

[0059] Varying CM or other materials were injected into the tail vein ofanesthetized Sprague Dawley rats (300-400 mg). The CM tested wereIOXAGLATE and IODIXANOL. Both are CM dimers and IOXAGLATE is ionic andIODIXANOL is nonionic. The CM injections were done 12 to 14 days aftersensitization of the rats by intraperitoneal injections of 1 mg ofovalbumin in normal saline. A Propaq blood pressure apparatus wasconnected to polyethylene catheters inserted into a carotid artery tomonitor mean arterial blood pressure. Injection rates were 6 ml/kg/min.The CM were injected I.V. either 6 hours before, 45 minutes before,concurrent with, or 10 minutes post challenge of a dose of 10 mg ofovalbumin. Saline injections, equiosmolar to the CM and injected at thesame time intervals served as controls.

[0060] In the absence of contrast media the ovalbumin injectionsinvariably resulted in a fall in blood pressure (anaphylactic shock)that reached a nadir at about 10 minutes and remained at this level, orslowly rose towards normal. When these studies were repeated in thepresence of a contrast media dimer (IODIXANOL or IOXAGLATE) orequiosmolar saline, the contrast media, injected 6 hours before, 45minutes before, concurrently, or 10 minutes after the ovalbumin contrastmedia produced a more rapid return of the blood pressure to normallevels than did the saline (FIG. 5 shows blood pressure tracings whenthe C.M. and Ovalbumin were injected concurrently and FIG. 6 showseffect when the Ovalbumin and C.M. were injected 10 minutes after the BPnadir).

Example III Effects of Monomeric or Dimeric Nonionic CM on Lethality ofIonic Media

[0061] The concept was also tested by examining the potential of amonomer nonionic contrast and a dimer nonionic contrast to diminish thelethality in 300-350 g Sprague-Dawley rats of an ionic monomer CM. Thenonionic monomer used was IOVERSOL (Optiray 160, Mallinckrodt; St LouisMo.). The nonionic dimer used was IOTROLAN (Isovist, Schering, Berlin,Germany). The ionic contrast media used was 70% methylglucamineiothalamate (Conray, Mallinckrodt; St Louis Mo.). An LD-100 techniquewas used to determine lethality. This technique involves an immediatedecision on mortality and is more humane than the LD-50 technique sincethe animals do not undergo post technique morbidity for variableperiods. The determination of death in this technique is done by acontinuous I.V. infusion of CM and noting at what dose the animalsuspended respirations for a period of at least 15 seconds. For CMtoxicity studies the technique correlated well with published data usinga standard LD-50 technique.

[0062] The results below shows that replacing 30% saline with 30% C.M.(nonionic) actually lowers mortality rather than increasing it. ExampleIII demonstrates that when either the monomer nonionic or the dimernonionic, both of which exhibit stronger binding potential toimmunoglobulins than does the ionic monomer used, are substituted forsaline, the lethality of the mixture diminishes (the animals can acceptmore total contrast media before lethality). This can now be assumed tobe due to the nonionic CM partially blocking the effect of the ionicmedia on IgE immunoglobulins and mast cell release.

[0063] S.D. Rats—LD₁₀₀ (gl/kg) LD₁₀₀ P 1) 30% OPTIRAY (nonionic) & 70%22.2 ± 1.9 (3) .003 CONRAY (ionic) 2) 30% Saline* & 70% CONRAY 16.4 ±0.8 (4) 3) 30% ISOVIST (nonionic) & 70% 23.7 ± 1.4 (3) .01 CONRAY(ionic) 4) 30% Saline* & 70% CONRAY 17.9 ± 1.7 (3)

Example IV Passive Cutaneous Anaphylaxis

[0064] In a further test of the ability of appropriate contrast media tomitigate ongoing antigen-antibody reactions, a passive cutaneousanaphylaxis (PCA) experiment was performed in rats.

[0065] In this Example, rats were injected intradermally with 50 μL ofserum from ovalbumin sensitized rats and varying mixtures ofNa/meglumine iothalamate (MD-76; 370 mg iodine/ml, Mallinckrodt) andnormal saline to a total of 50 μl. This was followed in 5-7 hours byintravenous injections of 1 mg ovalbumin along with Evans Blue and thenmeasurement of the subsequent extravasation of the blue coloring in thearea under the skin. Evans Blue binds to serum albumin and the diameterof the area of blue indicates extravasation of albumin secondary tospecific antigen-antibody reactions. The experiment showed that diluteintradermal concentrations of the contrast media appeared to accentuatethe permeability change, whereas concentrations greater than 20%progressively inhibited the permeability (presumably by “pseudoantigen”excess). In this case, where large amounts of CM are available due tolocal deposition, even an ionic monomer was sufficient to block specificantibody-antigen reactivity (see Table III below). TABLE III PassiveCutaneous Anaphylaxis Site # μl CM μl Saline μl Sensitized serum Stain(mm ± S.E./10) 1 50 0 50 7.5 ± 7 2 40 10 50 10.0 ± 10 3 30 20 50 17.5 ±10 4 20 30 50 62.5 ± 28 5 10 40 50  115 ± 60 6 0 50 50 87.5 ± 31

[0066] Controls with nonsensitized serum (3 rats) and 0, 25, and 50 μlCM showed no stain. Controls (4 rats) with sensitized serum and 1.9%saline replacing CM produced no stain at site 1, and 55 mm and 50 mmstains at sites 3 and 5. Other sites were not tested.

[0067] Significant differences (Student t-test): 2 vs. 4 (0.004), 2 vs.5 (0.0002), 2 vs.6 (0.00004)

Example V Protective Effects of CM on Experimental AllergicConjunctivitis

[0068] In this Example, the potential protective effect of a contrastmaterial on experimental allergic conjunctivitis induced in rats wasexamined. The rats were sensitized systemically to either ovalbumin orragweed pollen and 10 to 12 days later obtained local senitization byseveral applications of the respective antigens to the eyes. The ratswere then challenged with a larger dose of the antigen accompanied byeither the contrast media or equiosmolal saline and sacrificed atseveral different time periods for examination of the excised eyes.

[0069] The most reliable indicator of conjunctivitis was found to be acellular infiltration in the conjunctiva and/or in the underlying laminapropria. The tissues were examined on a “blinded” basis and assigned a 0to 3+ rating based on the perceived abundance of inflammatory cells(mostly lymphocytes, but also including eosinophils, polymorphonuclearleukocytes, and mast cells). The ovalbumin experiment was carried out at3 hours post antigen application (8 rats) and at 24 hours postapplication (8 rats) and the ragweed study was carried out at 1 hourpost application (8 rats) and at 24 hours post application (8 rats). Thecumulative scores for the ratings in each set of rats were recorded.Details of the ovalbumin study are as follows.

[0070] 16 male Sprague-Dawley rats (approximately six weeks old) weregiven IP injections of 1 ml of 1 mg/ml ovalbumin (Sigma) in normalsaline, containing 20 mg alum (Sigma) on Day 1 and on Day 2. On Day 11,10 μl of DTT (a dispersing agent) (Sigma) at 1 M in saline was appliedto both eyes, followed by 20 μl of saline to the control (left) eye and20 μl of IODIXANOL (Nycomed; Oslo, Norway). 15 minutes later, both eyeswere treated with DTT and then ovalbumin (20 μl of 1 mg/ml ovalbumin insaline). This process was done four times at 15 minute intervals. Theinterval between DTT and treatments was approximately 3-5 min. for eachrat. 8 rats were observed for 3 hours afterwards and 8 for 24 hours.

Results Ovalbumin Sensitized Rats

[0071] 2 HOUR READING: 24 HOUR READING saline + ovalbumin 8+ saline +ovalbumin 11+ CM + ovalbumin 1+ CM + ovalbumin  5+

[0072] A ragweed pollen experiment also involved 16 Sprague-Dawley ratsborn approximately 2 months previously and sensitized on Day 1 with SQinjections of 0.1 ml of N. saline containing 100 μg of ragweed pollen(P-0146, Sigma) and 20 mg alum. On Day 14, 20 μl of saline (left eye) or20 μl of IODIXANOL (right eye) were applied to the eyes. 15 min. later,both eyes were treated with 10 μl of phosphate buffered salinecontaining 1.5 mg of ragweed pollen. The process was done 4 times at 15min. intervals. 8 rats were observed for 1 hour preceding sacrifice and8 for 24 hours.

Results Ragweed Pollen Sensitized Rats

[0073] 1 HOUR READING: 24 HOUR READING saline + ragweed 0 saline +ragweed 15+ CM + ragweed 0 CM + ragweed  8+

[0074] It was also of interest that there were no absolute zeros in thesaline group while there were 3 zeros in the IODIXANOL group and theonly 3+ scores recorded were in the saline group. For the combinedovalbumin and ragweed pollen 24 hour studies, the CM differed fromsaline by P=0.068 (Student two tailed t-test).

Example 6 Protective Effects of Contrast Media on Allergic Rhinitis

[0075] Sprague Dawley rats were given an IP injection of 1 ml of 1 mg/mlovalbumin in normal saline containing 20 mg alum (reconstituted aluminumhydroxide gel). 10 days later, 8 of the rats were given 20 μl of salinemade equiosmolal to IODIXANOL into both nostrils via a small catheterplaced just inside the nostril and 8 rats were given 20 μl of IODIXANOLinto both nostrils. 15 minutes later, the animals were challengedlocally by installation of 20 μl of 1 mg/ml ovalbumin via the catheterinto each nostril.

[0076] The animals were then available to test for the quantity ofsecretion escaping from each nostril utilizing the method described byNamimatsu A. et al. (A New Method of the Measurement of Nasal Secretionin Guinea Pig, Int Arch Allergy Appl Immunol 1991, 95, 29-34) which ishereby incorporated by reference. In this method, a piece of cottonthread dyed with fluorescein at one end is inserted into the anteriorend of the nostril and kept there for 60 seconds. The stretch of colorresulting will be proportional to the fluid volume of the secretion aswill be the increase of weight of the thread. It is expected that thenoses pretreated with the IODIXANOL will show significantly lesssecretion with this model than will the noses pretreated with saline.For example, it is expected that the noses pretreated with saline willshow a stretch of color averaging about 20 to 40 mm while the nosespretreated with IODIXANOL will probably average 10 to 20 mm, reflectingthe inhibition of the locally applied allergen due to the antigen-excessphenomenon of the CM.

[0077] Similar studies will be carried out to examine the cellularchanges resulting when the animals are pretreated and challenged asabove, except that the pretreatment and challenge will be carried outfor a period of 3 days. 24 hours later the animals will be sacrificed.The head of each rat will be removed and fixed in formalin for 3 daysand then decalcified (5% trichloroacetic acid for 5 days). The nasalseptal mucosa will then be examined for eosinophilic infiltration. It isexpected that the rats receiving the IODIXANOL pretreatment precedingovalbumin challenge for each of the 3 days will exhibit lesseosinophilic infiltration in the mucosal tissues than will the ratspretreated with saline. For example, it is expected that the salinepretreatment will show an average of about 40-60 eosinophils/oilimmersion objective field counted on both sides of the septal cartilagewhile the IODIXANOL pretreatment group will show a much smaller average.In the nasal areas as in most other tissues in the body, theinfiltration of eosinophils is an index of a hypersensitivity response.

[0078] From all the above experimental results, it is concluded thatX-ray contrast media, to varying degrees, have the potential to serve asuniversal antigens that we have labeled “pseudoantigens.” This propertyappears to derive from the fact that all of the contrast media have thepotential to exist in an aggregated state that is greater in increasedconcentrations. In this aggregated state, contrast media assume the roleof multivalent antigens and can successfully compete with, and thusinhibit, any other antigens involved in antibody-antigen reactions thatmight lead to anaphylaxis. In this competition, the large quantity ofcontrast media that can be made available enables the media to functionin an antigen-excess mode that then inhibits the adverse effects whichwould otherwise result from the specific antibody-antigen reaction.

What is claimed is:
 1. A method of treating or preventing an allergicreaction in a mammal suffering from or susceptible to an allergicreaction, comprising delivering an X-ray contrast media to the mammal.2. The method of claim 1, wherein the X-ray contrast media is deliveredto the eye of a mammal and the allergic reaction is allergicconjunctivitis.
 3. The method of claim 2, wherein the administrationstep comprises administering from 0.1 to 3 ml of said X-ray contrastmedia.
 4. The method of claim 1, wherein the allergic reaction isallergic rhinitis.
 5. The method of claim 4, wherein the X-ray contrastmedia is delivered intranasally.
 6. The method of claim 4, wherein theadministration step comprises administering from 0.1 to 3 ml of theX-ray contrast media.
 7. The method of claim 1, wherein the X-raycontrast media is selected from the group consisting of a dimericnonionic contrast media and a deiodinated nonionic contrast mediaderivative.
 8. The method of claim 1, wherein the X-ray contrast mediais in a dimer form.
 9. The method of claim 1, wherein the X-ray contrastmedia is non-ionic.
 10. The method of claim 1, wherein the X-raycontrast media is in an aggregated form.
 11. The method of claim 1,wherein the X-ray contrast media is delivered in a manner selected fromthe group consisting of intranasally, subcutaneously, intramuscularly,intravenously or topically.
 12. The method of claim 1, wherein the X-raycontrast media comprises triiodinated, completely or partiallysubstituted, benzene moieties existing in the form of a monomer or adimer.
 13. The method of claim 1, wherein the X-ray contrast mediainhibits, treats or prevents an allergic reaction by blocking adverseantigen-antibody complex formation.
 14. The method of claim 13, whereinthe antibody is selected from the group consisting of IgA1, IgA2, IgD,IgE, IgG1, IgG2, IgG3, IgG4 and IgM.
 15. A method of preventing adversein vivo antigen-antibody complex formation by administering an X-raycontrast media to a person.
 16. The method of claim 15, wherein theadministration comprises the delivery from 0.1-40 grams of the X-raycontrast media.
 17. The method of claim 15, wherein the X-ray contrastmedia is a dimeric nonionic contrast media.
 18. A method of treating ofpreventing or treating allergic conjunctivitis comprising the step ofadministering from 0.1 to 3 ml of a dimeric nonionic X-ray contrastmedia to an eye of a mammal suffering from allergic conjunctivitis. 19.The method of claim 18 wherein the X-ray contrast media is selected fromthe group consisting of IOTROLAN and IODIXANOL.
 20. A method of treatingallergic rhinitis comprising administering from 0.1 to 3 ml of a dimericnonionic X-ray contrast media by drop installation into the nose in amammal suffering from allergic rhinitis or exposed to a known potentialnasal allergen.
 21. The method of claim 20, wherein the X-ray contrastmedia is selected from the group consisting of IOTROLAN and IODIXANOL.